The present invention relates generally to a system for acoustical reproduction of stereophonic signals and, more particularly, to a stereo signal reproducing system provided with delay unit for simulating the effect of acoustic reverberation.
With respect to conventional audio ambience simulation system, Japanese Patent Application (tokugansho) No. 59-237946 exemplifies such a system. The system comprises reproduction apparatuses and a delay circuit. One apparatus reproduces a signal output by a sound signal source, such as a disc record player, or so forth, while another apparatus delays the same signal by means of the delay circuit. The delayed signal is added to the signal without any delay (this will be referred as "dry signal"). The delay time is set within the range of 0.5msec. to 50msec. The system thus provides a signal which simulates the effect of acoustic reverberation so as to enhance the original signal output of the stereo. Acoustical ambience effect can thus be improved.
Such conventional systems, however, merely add a delayed signal which has a delay time in the range from 0.5msec. to 50msec. to a dry signal without regard to the reverberation characteristics of the listening chamber, because the acoustical properties of the chamber are not usually known. Therefore, even if the delay setting produces the optimum effect in a chamber having a certain set of acoustical properties, the same delay setting may provide an undesirable effect in another chamber having different acoustic qualities.
In practice, a delayed sound reaches the listener after the level of the natural reveberation from dry sound is reduced below a level required for acoustic ambience effect to be generated and thereby an acoustic separation of the delayed sound and the dry sound is caused. Since vehicular cabins have greatly different reverberation characteristics compared to most other normal audio chambers, such acoustic separation tends to occur in vehicular cabins especially. For these reasons, a system which creates an appropriate stereophonic sound ambience is sought.